title: Isokinetic concentric quadriceps and hamstring normative data for elite collegiate American football players participating in the NFL Scouting Combine.
abstract: Isokinetic concentric quadriceps and hamstring strength data using a Cybex dynamometer are collected for elite collegiate American football players invited to the annual National Football League Scouting Combine. We constructed a normative (reference) database of the Cybex strength data for the purpose of allowing comparison of an individual's values to his peers. Data reduction was performed to construct frequency distributions of hamstring/quadriceps (H/Q) ratios and side-to-side strength differences. For the cohort (n = 1,252 players), a statistically significant but very small (1.9%) mean quadriceps strength preference existed for dominant side vs. nondominant side. Peak torque (Newton meters, best repetition) for quadriceps and hamstrings was significantly correlated to player body mass (weight) (the same relationship was found for other variables using peak torque in the calculation). Peak torque varied by player position, being greatest for offensive linemen and lowest for kickers (p < 0.0001). Adjusting for body weight overcorrected these differences. The H/Q ratios and frequency distributions were similar across positions, with a mean of 0.6837 ± 0.137 for the cohort dominant side vs. 0.6940 ± 0.145 for the nondominant side (p = 0.021, n = 1,252). Considerable variation was seen for dominant-to-nondominant side difference for peak torque. For quadriceps, 47.2% of players had differences between -10% and +10%, 21.0% had a peak torque dominant-side deficit of 10% or greater compared to nondominant side, and for 31.8% of players, dominant-side peak torque was greater than 10% compared to nondominant side. For hamstrings, 57.0% of players had differences between -10% and +10%, 19.6% had a peak torque dominant-side deficit of 10% or greater compared to nondominant side, and 23.4% of players, dominant-side peak torque was greater than 10% compared to nondominant side. We observed that isokinetic absolute strength variables are dependent on body weight and vary across player position. The H/Q ratios vary only within a relatively narrow range. Side-to-side differences in strength variables >10% are common, not the exception.
authors.affiliation: 1UHZ Sports Medicine Institute, Doctors Hospital, Baptist Health South Florida, Coral Gables, Florida; 2Sports Medicine and Performance, Tampa, Florida; 3Rehabilitation, Tampa Bay Buccaneers, Tampa, Florida; and 4Orthopaedic Surgery, Johns Hopkins Hospital School of Medicine, Medstar Good Samaritan Hospital, Baltimore, Maryland.
authors.forename: John E
authors.initials: JE
authors.lastname: Zvijac
authors.forename: Todd A
authors.initials: TA
authors.lastname: Toriscelli
authors.forename: W Shannon
authors.initials: WS
authors.lastname: Merrick
authors.forename: Derek F
authors.initials: DF
authors.lastname: Papp
authors.forename: Gary M
authors.initials: GM
authors.lastname: Kiebzak
mesh_terms: D000328:Adult; D000886:Anthropometry; D056352:Athletes / Q000706:statistics & numerical data; D001265:Athletic Injuries / Q000517:prevention & control; D054874:Athletic Performance / Q000502:physiology*; D001696:Biomechanical Phenomena; D001835:Body Weight; D015331:Cohort Studies; D016001:Confidence Intervals; D016208:Databases, Factual; D005538:Football / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology*; D053581:Muscle Strength Dynamometer; D052097:Quadriceps Muscle / Q000502:physiology*; D012016:Reference Values; D014481:United States; D055815:Young Adult